The present invention disclosed herein relates to a vinyl chloride-based resin having excellent low viscosity characteristics and a method of preparing the same, and more particularly, to a method of preparing a vinyl chloride-based resin, in which two or more seed particles having different average particle diameters are used as a seed for a seeded emulsion polymerization method and low viscosity characteristics at low and high shear rates may be obtained by controlling the particle size of the seed having a smaller particle size.
With respect to a typical paste resin used for flooring material foaming, two or more particles having different sizes (large/small) are generally used to have low viscosities at low and high shear rates, and therefore, ease of processing may be provided.
Micro-suspension polymerization and seeded emulsion polymerization have been used as a method of polymerization of the paste resin used therein. With respect to micro-suspension polymerization, two or more vinyl chloride resin latexes having different sizes are generally used through mixing because the control of a particle size distribution is difficult. Production costs may be high because a reaction time is also longer than that of seeded emulsion polymerization. Different seed particles, generally two types of seeds, are used as a seed for the seeded emulsion polymerization, in which a small seed is prepared by emulsion polymerization and a large seed is prepared by micro-suspension polymerization. Monomer droplets are prepared by using a homogenizer, in which a vinyl chloride-based monomer, an emulsifier, an oil-soluble polymerization initiator are added and pressure is applied, or a rotor-stator type homogenization pump in terms of centrifugal force, and the large seed is then prepared by polymerization thereof.
Since the seeded emulsion polymerization is performed by using different seed particles, particle size control may be facilitated. However, a particle diameter of a final product may greatly depend on particle sizes of the large seed prepared by the micro-suspension polymerization and the small seed prepared by the emulsion polymerization. Typically, a large seed having a size range of 0.5 μm to 0.8 μm and a small seed having a size range of 0.08 μm to 0.13 μm have been used.
In the seeded emulsion polymerization, viscosity and foaming properties are controlled by controlling a ratio between the large seed and the small seed. Herein, the size of the small seed and a content thereof introduced in the seeded emulsion polymerization may significantly influence viscosity and foaming properties, such as foamed cell density, resilience, and whiteness.
Excellent foam properties may typically be obtained when the small seed is introduced in an amount of 2.5 ppm or more. However, since typically used small seed particles having a size range of 0.08 μm to 0.13 μm deteriorate low shear viscosity, the introduction thereof may be limited. The reason for this is that limitations in plastisol mixing and pumping may be generated in a production plant.